Research on Asteroids of Christian Ludwig Gerling and His Students In
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Journal Title XX(X):2–19 Research on asteroids c The Author(s) 2017 Reprints and permission: of Christian Ludwig sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/ToBeAssigned Gerling and his www.sagepub.com/ students in the nineteenth century Julia Remchin Independent Scholar, Germany Andreas Schrimpf Philipps–Universitat¨ Marburg, Germany Abstract One of the mayor topics in astronomy at the beginning of the 19th century was the interpretation of the observations of the first asteroids. In 1810 Christian Ludwig Gerling at the age of twenty two came to Gottingen¨ University to continue his academic studies. Supervised by Carl Friedrich Gauß at the observatory he was engaged in studies of theoretical and practical astronomy. Starting in 1812 Gerling accepted the responsibility for collecting observational data of the asteroid Vesta from the European observatories and for calculating the ephemeris of this new minor planet. In 1817 Gerling was appointed professor at Marburg University. One of his early astronomical projects in Marburg was his contribution to the arXiv:1903.12544v1 [physics.hist-ph] 29 Mar 2019 Berliner Akademische Sternkarten. After completion of his observatory in 1841 Gerling’s students started observing and theoretically analysing the orbits of the continuously newly discovered asteroids including the perturbation of the larger solar system bodies. The observations at Gerling’s observatory are the first astrometric measurements of solar systems minor bodies of Hesse. Keywords Asteroids, star maps, orbit calculation of asteroids, astronomy in the nineteenth century, Gerling-Observatory, Marburg Prepared using sagej.cls [Version: 2016/06/24 v1.10] 2 Journal Title XX(X) Introduction The starry sky was and still is fascinating. Since ages all cultures have been studying the motions of stars and solar system bodies. At the edge of modern ages based on observations without telescopes the positions and motions of Sun, Moon and the planets could be predicted with considerable precision. Kepler’s laws and the development of telescopes increased the knowledge of the orbits of solar system bodies to a great extend leading to a new view of world, the Copernican system, which finally became accepted after the publication of Newton’s law of gravity. The discovery of Uranus, the seventh planet, in the year 1781 by Wilhelm Herschel triggered an euphoric search for further solar system bodies. In fact, the first four asteroids were discovered at the beginning of the nineteenth century between 1801 and 1807 and the story of their discovery was studied and told by many authors from the very beginning, see for example G. Jahn 1, to a very recent and very detailed exploration by C. Cunningham. 2 The orbits of the first four asteroids roughly are located at the same region between Mars and Jupiter. The sizes of these asteroids were not known at that time so they were reckoned as ordinary planets. But this clearly opened a new problem: the Titius– Bode law 3 predicted one planet between Mars and Jupiter not four. Were the asteroids fragments of a former collision? To answer these questions further observations seemed to be necessary. All observatories in Europe monitored the new four planets. Besides Carl Friedrich Gauß his students Friedrich Bernhard Gottfried Nicolai, Johann Franz Encke, Friedrich Ludwig Wachter, Christian Ludwig Gerling and August Ferdinand Mobius¨ calculated new orbital elements and ephemerides. Wachter and Mobius¨ took care of Juno, Encke was responsible for Pallas and Gerling was busy with Vesta. 4 It was clear, further solar system bodies had to be less bright than the ones known, otherwise they would have been detected till then. Therefore one of the major demands was the improvement of star charts, i.e. less bright stars should be included. The catalogues of Jer´ omeˆ Lalandes, the Histoire Celeste,´ and Giuseppe Piazzi increased the number of recorded stars to about 50,000. 5 However, those catalogues were not complete, they did not contain all stars down to a certain brightness. Hence in 1824 Friedrich Wilhelm Bessel initiated the compilation of the Berliner Akademische Sternkarten 6, thus supporting the search for new smaller solar system bodies. For many years following 1807 no new minor planet was discovered. Then, in December 1845, 38 years after the first observation of Vesta, Karl Ludwig Hencke discovered the fifth minor planet Astraea. Though the new solar system bodies are much Corresponding author: Andreas Schrimpf, History of Astronomy and Observational Astronomy, Philipps-Universitat¨ Marburg, Renthof 7b, D-35032 Marburg, Germany. Email: [email protected] Prepared using sagej.cls Remchin and Schrimpf 3 smaller than any other planet, they had been counted as regular planets. When Neptune was discovered in 1846 it became the 13th planet of our solar system. 7 In July 1847 the sixth minor planet was discovered, and then no year passed without new discoveries. Accepting the proposal of Alexander von Humnboldt 8 in 1851 a new class of solar system bodies, finally was introduced. The minor planets were named asteroids, just as Herschel had suggested already in 1802. With the increasing number of discovered asteroids and the increasing precision of observations the perturbations of the large solar system bodies on the orbits of the asteroids came into focus, which finally lead to the discovery of the Kirkwood gaps and the chaotic properties of asteroids in the main belt. 9 In this paper we will review the up to day somewhat overseen contribution of Christian Ludwig Gerling in the beginning of the research on asteroids. His ephemeris calculations have been shortly summarized by G. Jahn 10 and were cited by C. Cunningham. 11 However his contributions to the improvement of the star maps and his observatory at Marburg and the observations of his students in the mid of the 19th century as well as the theoretical investigations of perturbations of the larger planets on the orbits of smaller asteroids were not recognized so far. The paper presented here is based on publicly available information and the scientific estate of Chr. L. Gerling containing his correspondence and notes. 12 Christian Ludwig Gerling Christian Ludwig Gerling (Fig.1) was born in Hamburg, Germany, in 1788 as a son of a preacher. His education started with private lessons at home and continued at the grammar school “Johanneum”, Hamburg, together with his long–time friend Johann Franz Encke. After school Gerling registered at the University of Helmstedt, Lower Saxony, for theology. In addition he attended lectures in mathematics of professor Pfaff. In 1810 the University of Helmstedt was closed and Gerling decided to continue his academic studies in mathematics and astronomy in Gottingen.¨ At the observatory he kept himself busy with theoretical and practical astronomy under supervision of Carl Friedrich Gauß and Karl Ludwig Harding. 13 There he got to know Gottfried Nicolai, who later became director of the observatory in Mannheim, Germany, and Friedrich Ludwig Wachter. Encke joined this group in 1811. He later became director of Seeberg Observatory, Gotha, and finally in 1825 of the Berlin Observatory. Studying under Gauß Gerling not only learned the appropriate use of instruments but also the mathematical methods for analysis of geodetic and astronomic measurements. Later, Gerling published among others a book about the practical use of least squares in geodetic data analysis. 14 In 1812 Gerling finished his doctoral thesis about a calculation of the path of the solar eclipse in 1820 in northern Europe. After he received his PhD Gerling entered a position at a high school in Kassel, Hesse. At that time he used a small observatory in Kassel for astronomical observations. He continued to seek a university position and finally in 1817 was appointed full professor of mathematics, physics and astronomy and director of the ”Mathematisch–Physikalisches Institut” at the Philipps–Universitat¨ of Marburg. In Prepared using sagej.cls 4 Journal Title XX(X) Figure 1. Christian Ludwig Gerling (1788-1864) spite of several offers he remained at the university in Marburg till his death in 1864. 15 During his career three times he kept the position as prorector of the university, he was representative in the chamber of the Electorate of Hesse and in 1857 he was appointed court counsellor. Due to his scientific reputation he was nominated member of several scientific societies, e.g. the Gottingen¨ Royal Society of Sciences. 16 Gerling’s scientific work in Marburg was affected by two major topics: in his early period from 1817 to 1838 he was well occupied with organizing the triangulation of Kurhessen. 17 During that time Gerling did not have an observatory, so his astronomical work was reduced mainly to corrections and additions on a section of Encke’s “Berliner Akademische Sternkarten”. In 1838 the institute moved to a new home in Marburg at the ”Renthof”. After the building was reconstructed in 1841, he could finally put into operation his new but small observatory, built on top of a tower of Marburg’s old city wall. 18 Gerling pursued the scientific topics of astronomy of that time, making meridional observations and differential extra–meridional measurements of stars, planets and asteroids, observations of lunar occultations, as well as astronomical time determinations mainly to improve the precision of star catalogues, improving orbital parameters of solar system bodies and the solar parallax. Carl Friedrich Gauß and Christian Ludwig Gerling started their relationship as a teacher and his student but during the following years they became each others counsellor and finally close friends. Their correspondence not only contains details of scientific discussions but also reflects their close relationship. 19 Gerling infected his students with his enthusiasm for astronomy: Carl Wilhelm Moesta became the first director of the National Observatory of Chile, 20 Eduard Schonfeld¨ became director of the observatory in Mannheim, Germany, and later the successor of Friedrich Wilhelm August Argelander Prepared using sagej.cls Remchin and Schrimpf 5 in Bonn, and Ernst Wilhelm Klinkerfues became assistant and later successor of C.F.